Extending Your Display on a Mac


Extending your display allows a second display to show something different from what your computer’s screen shows. This is different from mirroring your displays, which shows an exact copy of your computer’s screen.

  1. Ensure your projector or display is turned on and connected to your computer
  2. Select System Preferences in the Apple menu, then click Displays
  1. Select the Arrangement tab

  2. Uncheck Mirror Displays

  3. The projected screen should now show an empty desktop background

  4. You can arrange your displays in a way that feels most natural to you by dragging the blue screens in the center of the menu.

  5. The screen with the white tool bar is your home screen.

  6. The two images to the left show an example of changing an extended display from the left side of your home screen to the right.

  7. If you need to determine which screen you are dragging. Click on the screen and a red border will appear around the clicked display.


Matching the Resolution of Displays

It is likely that by default, your computer has a resolution that is different from the default resolution of your projector. For the projected tab to accurately mirror what’s on your computer screen, it’s recommended that you change the resolution settings so both displays have a similar resolution.


To see possible resolutions for your computer’s display:

  1. Click the Apple menu in the top left corner of your screen > System Preferences, click Displays, then select the Display tab.

  2. Select Scaled, then hover over the options to see the various resolutions.


To see possible resolutions for your projected display:

  1. Click the Gather Windows button, this will bring the display settings window for your projected display behind the current window.

  2. Select the Display tab in the window for your projected display.

  3. Adjust the resolution of both displays to match them as closely as possible. Matching the first number (for the width) is more important than matching the second number for height. (See how number 2 and 6 match in the image above)

    • Press the Option key while you click the Scaled option to see additional resolutions for the second display. (See Step 5 in the image above)

NOTE: Depending on your operating system, there may also be settings to adjust the size of text, apps, etc. that should be checked to make sure there isn't a vast difference between your main screen and the student display. 


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